A case of congenital giant gallbladder with massive hydrops mimicking celiac cyst.

We present a case of a 55-year-old female who suffered from a mass in the right upper abdomen, which had been present for over six months. Pre-operative blood examinations, including tumor markers, were normal. Initially, the admitting diagnosis was a giant celiac cyst, due to its liquid cystic appearance and large size (approximately 30.0×18.0 cm), visible in the hepatic region under ultrasound. Following the discovery of a cystic duct during surgery, the diagnosis was corrected to be a giant gallbladder. As no obstructive matter was observed, the giant gallbladder was considered to be congenital.